The present invention relates to a ski binding. More particularly this invention concerns a safety ski binding for use both in cross-country skiing or in downhill skiing.
The main difference between the equipment used for cross-country skiing and for downhill skiing is in the bindings. For downhill skiing the skiboot is secured both at the toe and at the heel to the ski. On the contrary for cross-country skiing a walking maneuver must be possible so that the skiboot or the equivalent must be able to pivot on the ski about an axis which is perpendicular to the normal direction of travel of the ski and generally at the toe of the boot.
Double-duty ski bindings are known which can allow the skiboot to be secured at the toe and heel as for downhill skiing and can also allow it to pivot as for cross-country skiing (also known as touring skiing). Usually such a ski binding is also provided with means that release the skiboot when this boot stresses the toe or heel holders with greater than a predetermined force. Thus injury is avoided, as the skier's foot is freed from the ski in case of a spill.
A typical such double-duty ski binding has a plate which is hinged at its front end on the ski and which can be rigidly secured at its rear end to the ski. This plate carries conventional toe and heel holders, that is, clamps which engage over the toe and heel portions of the boot sole to secure this boot securely to the plate. Such an arrangement is relatively simple and uses conventional items. However it has the considerable disadvantage that the toe of the skiboot must be spaced relatively far from the hinge in order to accommodate between this toe and the hinge the relatively long toe holder. Thus during cross-country use the skier must pivot his skiboot about an axis relatively far from the tip of the ski, an extremely strenuous and tiring manner of skiing. Furthermore when the boot is so raised from the ski the likelihood of a spill is considerably increased.
Since much cross-country skiing is done in a camping context when the skier does not want to be burdened with skiboots only suitable for skiing, it is important to be able to use cross-country ski bindings with conventional heavy-duty hiking shoes. This is normally made possible by securing to such hiking shoes intermediate plates which are in turn fitted to the double-duty binding. Such an arrangement has the disadvantage of considerable extra cost and also elevates the boot relatively far from the ski, thereby increasing the difficulty of skiing.
Another difficulty with most of the known safety bindings is that the type of boot used changes the release force of the binding. This is mainly due to the fact that frictional forces between the boot and a surface of the binding frequently are a considerable factor in the force at which the binding releases so that relatively rough boots will release at a greater force and relatively smooth boots at a lesser force.
Double-duty ski bindings can be seen in German published specification No. 1,578,912 and in German patent specification open for inspection No. 2,213,354.